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Full text of "The manufacture and properties of iron and steel"

284
METALLURGY OF IRON AND STEEL.
a full heat wheri the interior is unaffected.. Since the manufacturer may always .manipulate the operation so as to affect the test-pieces in. preference to the rest of the steel, and since it will be to Ms interest to keep the temperature as low as possible to avoid warping, there will be no certainty either that the work has been properly carried out or that it has been of the least advantage.
SEC. XVg.—Further experiments on annealing rolled bars.—* The experiments on annealing related in this chapter were performed by the usual method of estimating temperatures by the eye. They were, however, conducted under conditions exceptionally favorable to uniform results, as the pieces were small and were enclosed in a muffle and were carefully watched. No ordinary an-
TABLE XV-J.
Effect of Annealing at about 800° 0. (1473° P.) on the Physical Properties of Structural Steel.    (Bars are rolled flats 2"x%".)
				•A •	2 ft	-*H	•H (4	
Limits of					i	•Sft	o a ft	d
Ulitimate Strength Ibs. per sq.	Kind of Steel.	No. of bars.	Condition of bar.		ISjj	.2 •-bftd*J	1:,-	s o
inch.				n&	sits*	Oflg	T3 M *> 0) 03 O	53
					•4 . "	S		f4
57 to 61,000	Acid open hearth.	10	Natural	60,110	39,770	33.3	52.0	66.1
		15	Annealed	55,690	36,180	36.3	56.8	64.9
56 to 64,000	Basic open hearth.	12	Natural	61.740	38,861	33.0	52.3	63 0
		• 17	Annealed	57,870	85,320	36.6	57.6	61.0
58 to 68, 000	"Transferred."	10	Natural	62,050	39.590	33.4	54.9	64.6
	See Section Xlla.	15	Annealed	55,590	34,790	37.3	59.0	62.6
nealing of eye-bars or plates would be carried out under such favorable auspices. For purposes of comparison, I 'have repeated some of the experiments, the temperatures being determined by the Le Ohatelier pyrometer. In Table XV-J it is shown that the heat treatment has reduced the tensile strength, the elastic limit and the elastic ratio, and has raised the elongation and reduction of area. In Table XY-K are compared the bars showing similar ultimate strength. The annealed pieces show greater elongation, but a lower elastic ratio, and in order to obtain the same elastic limit it would be necessary to take a harder steel, whereby the elongation would be somewhat lowered. It would seem doubtful therefore whether the bars under the most careful annealing are